The spindle moving device of the conventional drilling machine or drilling/tapping machine consists of a rack gear and a pinion meshed therewith. That is, a vertically movable tube is made to move up and down by manipulating a moving handle which is laterally connected to the pinion.
An automatic spindle moving device is disclosed in Japanese Utility Model Publication No. Sho-51-30064, and No. Sho-57-39127. In these devices, a separate pulley or a motor is used as the driving power source, and a plurality of worms and worm wheels have to be meshed to each other.
Further, as disclosed in Korean Utility Model Publication No. 1983-302 (which has almost the same constitution as that of Japanese Utility Model No. Sho-58-37526) and in Korean Utility Model Publication N.o 1979-1963, the clutch mechanism of the handle is complicated, and, if a fast moving is to be made possible, separate pneumatic and hydraulic cylinders are required as the driving means. Further, there are required an electronic circuit for controlling the pneumatic and hydraulic cylinders, an air compressor, a hydraulic pump, and hydraulic path tubes. Therefore, the device is magnified in its bulk, becomes complicated in its constitution, and is stepped up in its price.
Further, as disclosed in Japanese Utility Model Publication No. Sho-60-35532, a link or the like is used in moving the vertically movable tube up and down, and this has been the generally prevalent application.
For example, when drilling a hole into a work piece by a drilling machine, a large hole cannot be drilled at one time, and therefore, several rounds of drilling have to be performed starting from a small hole and increasing the size of the hole at each round thereafter in order to drill a single large hole. Further, when drilling holes repeatedly to the same depth, the descending level of the spindle has to be indirectly adjusted by bringing down the spindle to the bottom by means of a manual handle, and by adjusting the tip of the drilling tool to the work piece. Further, when drilling a deep hole, if the drilling is carried out continuously, the spaces around the drilling tool is filled with the chips, thereby increasing the drilling resistance. Consequently, the drilling tool can be broken off, or can be heated to such a degree that the life expectancy of the drilling tool is shortened. If such a phenomenon is to be avoided, the drilling has to be performed several times step by step. As the hole is drilled deeper and deeper, the spindle moving handle has to be pulled down alternately with the other hands, with the result that the drilling operation becomes very troublesome.
Particularly, in the case where the work piece is composed of copper or aluminum, a cooling fluid has to be supplied by one hand and so on, with the result that the work efficiency is significantly decreased.
Meanwhile, when carrying out a tapping, the tapping tool has to be brought down to the work piece by manipulating the moving handle, and, once the tapping tool enters into the hole to be tapped, the tapping tool itself advances within the hole in order to form threads, without requiring further manipulating of the moving handle. However, when tapping threads of small pitches, if the tapping tool is let to advance for itself within the hole, a precision tapping cannot be performed, and, on the other hand, even if the moving handle is manually manipulated, the moving speed becomes non-constant, with the result that the internal threads thus formed cannot be firmly coupled with a bolt.